/* strnatcmp.c
 *
 * Original code downloaded from: http://sourcefrog.net/projects/natsort/

  strnatcmp.c -- Perform 'natural order' comparisons of strings in C.
  Copyright (C) 2000, 2004 by Martin Pool <mbp sourcefrog net>

  SPDX-License-Identifier: Zlib
 */


/* partial change history:
 *
 * 2004-10-10 mbp: Lift out character type dependencies into macros.
 *
 * Eric Sosman pointed out that ctype functions take a parameter whose
 * value must be that of an unsigned int, even on platforms that have
 * negative chars in their default char type.
 */

/*
 * Modified 2014-10-29 to use the g_ascii_XXX() routines; this avoids
 * locale-dependent behavior.  The routine names were changed to
 * ws_ascii_XXX() to reflect this.
 */


#include <glib.h>

#include "strnatcmp.h"


/* These are defined as macros to make it easier to adapt this code to
 * different characters types or comparison functions. */
static int
nat_isdigit(nat_char a)
{
    return g_ascii_isdigit(a);
}


static int
nat_isspace(nat_char a)
{
    return g_ascii_isspace(a);
}


static nat_char
nat_toupper(nat_char a)
{
    return g_ascii_toupper(a);
}


static int
compare_right(nat_char const *a, nat_char const *b)
{
    int bias = 0;

    /* The longest run of digits wins.  That aside, the greatest
       value wins, but we can't know that it will until we've scanned
       both numbers to know that they have the same magnitude, so we
       remember it in BIAS. */
    for (;; a++, b++) {
        if (!nat_isdigit(*a)  &&  !nat_isdigit(*b))
            return bias;
        else if (!nat_isdigit(*a))
            return -1;
        else if (!nat_isdigit(*b))
            return +1;
        else if (*a < *b) {
            if (!bias)
                bias = -1;
        } else if (*a > *b) {
            if (!bias)
                bias = +1;
        } else if (!*a  &&  !*b)
            return bias;
    }

    return 0;
}


static int
compare_left(nat_char const *a, nat_char const *b)
{
    /* Compare two left-aligned numbers: the first to have a
       different value wins. */
    for (;; a++, b++) {
        if (!nat_isdigit(*a)  &&  !nat_isdigit(*b))
            return 0;
        else if (!nat_isdigit(*a))
            return -1;
        else if (!nat_isdigit(*b))
            return +1;
        else if (*a < *b)
            return -1;
        else if (*a > *b)
            return +1;
    }

    return 0;
}


static int strnatcmp0(nat_char const *a, nat_char const *b, int fold_case)
{
    int ai, bi;
    nat_char ca, cb;
    int fractional, result;

    if (!a || !b) {
        if (!a && !b)
            return 0;
        if (!a)
            return -1;
        return +1;
    }
    ai = bi = 0;
    while (1) {
        ca = a[ai]; cb = b[bi];

        /* skip over leading spaces or zeros */
        while (nat_isspace(ca))
            ca = a[++ai];

        while (nat_isspace(cb))
            cb = b[++bi];

        /* process run of digits */
        if (nat_isdigit(ca)  &&  nat_isdigit(cb)) {
            fractional = (ca == '0' || cb == '0');

            if (fractional) {
                if ((result = compare_left(a+ai, b+bi)) != 0)
                    return result;
            } else {
                if ((result = compare_right(a+ai, b+bi)) != 0)
                    return result;
            }
        }

        if (!ca && !cb) {
            /* The strings compare the same.  Perhaps the caller
               will want to call strcmp to break the tie. */
            return 0;
        }

        if (fold_case) {
            ca = nat_toupper(ca);
            cb = nat_toupper(cb);
        }

        if (ca < cb)
            return -1;
        else if (ca > cb)
            return +1;

        ++ai; ++bi;
    }
}


int ws_ascii_strnatcmp(nat_char const *a, nat_char const *b)
{
    return strnatcmp0(a, b, 0);
}


/* Compare, recognizing numeric string and ignoring case. */
int ws_ascii_strnatcasecmp(nat_char const *a, nat_char const *b)
{
    return strnatcmp0(a, b, 1);
}


/*
 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 4
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * vi: set shiftwidth=4 tabstop=8 expandtab:
 * :indentSize=4:tabSize=8:noTabs=true:
 */

